Laminated unit

ABSTRACT

A laminated panel unit ( 1 ) comprising at least one image layer ( 3 ) between at least two panels ( 2 ), wherein for an area-contact gluing of the image layer ( 3 ) with neighboring panels ( 2 ), one intermediate adhesive layer ( 4, 4 ′) is provided on each side thereof, wherein the two intermediate adhesive layers and/or panels following each image layer ( 3 ) have a different thermal expansion behavior so that the image layer ( 3 ), due to the inhomogeneous laminate, is tensioned in case of temperature changes; as well as a method for producing a laminated panel unit ( 1 ), wherein the image layer ( 3 ) is connected with area contact on either side thereof with the panels ( 2 ) by using intermediate adhesive layers ( 4, 4 ′), the intermediate adhesive layers ( 4, 4 ′) and/or the panels ( 2 ) having a different thermal expansion behavior.

The invention relates to a laminated panel unit comprising at least oneimage layer between at least two panels, wherein for an area-contactgluing of the image layer with neighboring panels, one intermediateadhesive layer is provided on each side thereof, as well as to a methodfor producing the laminated panel unit according to the invention. Theimage layer may have any optic image desired, including particularlyalso writings.

From U.S. Pat. No. 5,595,794 A, a laminated glass unit is known inwhich, for keeping archives of photograph material, the photograph isglued between two glass panes by means of two adhesive polyurethanelayers, whereby a five-layer laminate is formed. However, such alaminated glass unit is only suitable for interior archiving, and eventhis to a limited extent only, since already with relatively slighttemperature fluctuations the adhesive polyurethane layers of thelaminated glass unit will expand upon heating, whereby the photographenclosed between the two glass panes will become wavy, resulting in anoptically negative, unacceptable change of the photograph materialenclosed in the laminated glass unit.

A somewhat different laminated panel unit which comprises a visible(motif) pattern is described in WO 95/00329 A1. A visible pattern isapplied to a plastics sheet, e.g. a polyvinyl butyral sheet, by means ofan epoxy-resin-based printing ink and is dried on the polyvinyl butyralsheet before the laminated unit is assembled. More precisely, an inklayer is used by silk-screening to produce a pattern, and only onesingle plastics sheet, i.e. polyvinyl butyral sheet, is used tointerconnect two glass panes or plastics panels.

JP 56-45852 A shows a method of producing stained glass, whereindepressions are technically produced in a resin layer in which finallythe desired dyes are injected.

It is now an object of the present invention to provide a laminatedpanel unit of the initially defined kind, which ensures an opticallyperfect rendering of the image layer enclosed between the panels even incase of temperature fluctuations. Therewith, in particular, also alaminated panel unit is to be created which can be used externally, e.g.as facade glass-work, windows and the like, and which will withstandalso the substantial temperature fluctuations occurring outside.Furthermore, it is an object of the invention to provide a method forproducing the inventive laminated panel unit.

The inventive laminated panel unit of the initially defined type ischaracterized in that the two adhesive intermediate layers and/or panelsfollowing each image layer have a different thermal expansion behaviorso that the image layer, due to the inhomogeneous laminate, is tensionedin case of temperature changes. With the help of the two layersneighboring the image layer (intermediate adhesive layer, panel), whosethermal expansion behavior differs, the image layer is held tensionedbetween the two panels even if the laminated panel unit is heated. Thus,the image layer enclosed between the two panels can be prevented frombecoming wavy, and also the formation of blisters can be avoided, sincethe different thermal expansions on the two sides of the image layerwill result in an inhomogeneous glass laminate in which merely a slightcurvature of the entire laminated panel unit will occur which, however,will have a negative effect neither on the optical appearance nor on theadhesive behavior of the image layer.

For an optically attractive appearance of the laminated panel unit, itis suitable if at least one panel is transparent or translucent,respectively.

For a laminated panel unit having a long useful life, it is advantageousif glass panes are provided as the panels.

An inhomogeneous laminate is reliably ensured if the two intermediateadhesive layers and/or panels are made of different materials, so thatduring a temperature change the enclosed image layer is continuouslysubjected to a tension, whereby waviness and blister formation,respectively, can be prevented.

In particular, the undesired waviness and blister formation,respectively, may reliably be avoided if the two intermediate adhesivelayers and/or panels are made of materials having different thermalexpansion coefficients. In this manner it will be ensured that the imagelayer will reliably remain tensioned by the intermediate adhesive layerand/or by the panel which has the higher thermal expansion coefficient,even when the laminated panel unit is heated, wherein a slight concavecurvature of the entire laminated panel unit will occur with regard tothe intermediate adhesive layer and/or to the panel having the higherthermal expansion coefficient.

Tests have shown that for avoiding waviness it is also suitable if thetwo intermediate adhesive layers have different gluing abilities, sincethus the image unit enclosed by the two intermediate adhesive layerswill be differently tensioned on either side.

To form an inhomogeneous panel/image layer/panel laminate, whereby acurvature of the entire laminated panel unit will occur instead of theimage layer enclosed between the panels becoming wavy, it is alsoadvantageous if the two intermediate adhesive layers and/or panels havedifferent material thicknesses. For instance, an inhomogeneous laminatewill also be created if the intermediate adhesive layers on both sidesare made of the same material, have the same thermal expansioncoefficient, yet the panels differ in material thickness.

It is preferred that at least one intermediate adhesive layer is asheet, preferably an ethylene vinylacetate copolymer (EVA) sheet,polyvinyl acetate (PVA) sheet, polyvinyl butyral (PVB) sheet or thelike. EVA sheets have proved successful in practice since, in contrastto the known polyurethane sheets, they do not require autoclaves forgluing the glass panel to the image layer. As ethylene vinyl acetatecopolymer sheets (EVA films), particularly sheets of Sekusui,Bridgestone and Takeda are preferred, the best results in terms oflaminate strength having been obtained with the S-LEX-EN film ofSekusui.

If one intermediate adhesive layer is made of a casting resin, areliable laminate of the image layer with the neighboring glass panewill be given, wherein, of course, the most varying types of castingresins may be used. In tests it has also been proved suitable that oneintermediate adhesive layer consists of silicone adhesive.

To prevent moisture from penetrating to the image layer that is enclosedbetween the panels, in which case the strength of the laminated panelunit would no longer be given and an undesired waviness of the imagelayer would occur, it is advantageous if on the periphery of the panels,at the narrow sides thereof, an external insulating layer, preferably ofsilicone, is provided.

If a photograph, a slide, an ink-jet, laser or silkscreen print or thelike is provided as the image layer, different laminated panel units inthe widest variations can be made, and because of the simple duplicationof photographs, ink-jet, laser prints and the like, the production ofthe laminated panel unit will be particularly cost-efficient.Particularly with a view to a long-lasting light-fastness of thelaminated panel unit, when using photographs as image layer, it isadvantageous if a photograph developed according to the silver-bleachingmethod (P3X-method) is provided. Here, preferably so-called“Ilfochromfotos” of the company Ilford which have been producedaccording to the silver-bleaching method, are used, since from all theknown photographic films, they are the most light-fast ones. Suchphotographs also have the advantage that they have polyester as carriermaterial, and consequently, together with the two adjacent (glass)panes, they will form an extremely resistant laminate, similar tobullet-proof glass. Likewise, the image layer increases the acousticinsulation of the (glass) panes, which makes them particularly suitableto be used as partition walls.

In order to achieve different optic effects with the laminated panelunit, it is suitable if the image layer is transparent, translucent oropaque. Here, the image layer may comprise the most varying carriermaterials, with the carrier material in case of a transparent ortranslucent image layer, respectively, mostly consisting of triacetateor polyester, whereas in case of opaque image layers, polyester sheetsor polyethylene paper is preferably used as the carrier material. Theinventive laminated panel unit may thus very well be used as a lightregulating means which regulates, or reduces, respectively, incidentlight.

If the laminated panel unit has an area of larger than 2 m², preferablylarger than 4.5 m², it may advantageously be used for externalapplications, such as facades, windows and the like, resulting in anattractive appearance for the viewer from the outside, with the incidentlight simultaneously rendering the motif of the image layer in theinterior space, similar to a slide projection.

The method for producing a laminated panel unit according to any one ofclaims 1 to 14 is characterized in that the image layer is connectedwith area contact on either side thereof with the panels by usingintermediate adhesive layers, the intermediate adhesive layers and/orthe panels having a different thermal expansion behavior. By thisproduction method in which intermediate adhesive layers and/or panelswith different thermal expansion behavior are used on either side of theimage layer, laminated panel units can be produced in which the imagelayer cannot become wavy or form blisters, respectively, even in case oftemperature changes, so that they may particularly also be used inexternal applications.

If the panels are glued together without the use of an autoclave, aproduction of laminated panel units is achieved which is much moreenergy-saving than known production methods in which the laminated panelunit is glued together by means of a polyurethane sheet in an autoclave.

For a reliable laminate of the image layer with the panels it isadvantageous if the laminated panel unit is glued together under anegative pressure. To increase the adhesion propensity of the imagelayer, it is advantageous if the image layer is cleaned, preferablydegreased, on either side prior to gluing.

For a simple and cost-effective production as well as for an easyapplication of a negative pressure for the gluing it is suitable if thegluing of the image layer with at least one panel is effected in aplastics envelope. In doing so, it is particularly suitable if theplastics envelope, prior to the gluing of the image layer to at leastone panel, preferably is evacuated to substantially 0.8 bar, wherebyadvantageously also the humidity in the plastics envelope is reduced. Ahigh proportion of moisture in the laminated panel unit is particularlydetrimental when using “Ilfochromfotos”, since by this thelight-fastness of the photographs is negatively affected.

If a casting resin is used as the intermediate adhesive layer, it isadvantageous if at first the image layer is merely connected to a firstpanel, preferably in a plastics envelope, and only in a second methodstep a second panel is connected thereto after the image layer has beenconnected to the first panel. Thus, after the first method step, a gluecan be applied in frame-like manner to the rim of the panel/imagelayer-laminate at the image-layer side thereof, whereby the second panelwill be kept in spaced relationship from the former under formation of acavity when being laid onto the image layer, and the cavity can befilled thereafter with casting resin.

When using sheets on both sides as intermediate adhesive layers, it issuitable with a view to an efficient, time-saving production of thelaminated panel unit if the image layer is connected simultaneously toboth panels.

In the following, the invention will be described in more detail andwith reference to preferred exemplary embodiments illustrated in thedrawings, to which, however, it shall not be restricted. In detail, inthe drawings

FIG. 1 shows a view of a laminated glass unit in an exploded, not yetassembled position;

FIG. 2 shows a view of the laminated glass unit in an assembledposition;

FIG. 3A shows a partial region of the section according to line III-IIIof FIG. 2;

FIG. 3B likewise shows a partial region according to section III-III ofFIG. 2, yet with a different intermediate adhesive layer; and

FIG. 4 shows a section of a laminated glass unit comprising two imagelayers.

In FIG. 1, a laminated glass unit 1 is shown in a not yet assembledposition, wherein the two glass panes 2 are visible between which animage layer 3 is glued by means of intermediate adhesive layers 4, 4′provided on either side of the image layer 3.

Prior to gluing of the image layer 3 which, preferably, is anIlfochrom-photograph, the former at first is degreased on either side soas to increase the gluing ability.

Then the image layer 3 is applied to the glass pane 2 with anintermediate adhesive layer 4 being interposed. Subsequently, the secondglass pane 2 is applied to the glass pane/image layer-laminate 1′ with asecond intermediate adhesive layer 4′ being interposed. The entire, notyet glued together laminated glass unit then is enveloped with aplastics envelope or sheet, respectively (not shown), and closed in anair-tight manner. Subsequently, a vacuum pump is connected to theplastics envelope, and in this manner a negative pressure ofapproximately 0.83 bar is produced. For gluing the image layer 3 to theintermediate adhesive layers 4, 4′, and for gluing the latter to theglass panes 2, the entire glass pane/image layer laminate is “baked” inan oven.

After termination of the gluing procedure and cooling of the laminatedglass unit, the plastics envelope is removed.

As an alternative to the simultaneous gluing of a glass pane/imagelayer/glass pane unit, at first the image layer 3 may also be merelycombined with a glass pane 2 into a laminate 1′, as sketched in FIG. 1by the broken partition line 5. After the image layer 3 has been gluedto a single glass pane 2, the second glass pane 2 can be put onto theimage layer side in spaced relationship by means of a frame-like appliedglue, and the enclosed cavity can be filled with a casting resin. Onlyin a second method step, the second glass pane 2 is then glued to thealready glued-together glass pane/image layer laminate 1′ with the helpof the second casting resin intermediate adhesive layer 4′.

Upon gluing, a laminated glass unit 1 forms, as shown in FIG. 2, with asilicone adhesive 7 being applied on the periphery of the glass panes 2after the narrow side 6 has been glued, so as to reliably preventmoisture from the outside from penetrating to the image layer 3 enclosedbetween the glass panes 2; too high a proportion of moisture in thelaminated glass unit would reduce the strength of the laminate, on theone hand, and, moreover, deteriorate the light-fastness of the imagelayer 3, if an Ilfochrom photo is used.

What is essential here is that the two intermediate adhesive layers 4,4′ schematically illustrated in FIGS. 3 a and 3 b consist of differentmaterials, since in this manner an inhomogeneous laminate is provided;whereby, when heating the laminated glass unit 1, an unintended waveformation of the image layer 3 between the two glass panes 2 isprevented. For an inhomogeneous glass pane/image layer/glass panelaminate, particularly the different thermal expansion behavior as wellas the different gluing abilities of the two intermediate adhesivelayers 4, 4′ with the image layer is responsible.

For a reliable gluing which, at the same time, does not negativelyaffect the light-fastness of the laminated glass unit, in particularsheets of ethylene vinylacetate compolymer (EVA), polyvinyl acetate(PVA) as well as polyvinyl butyral (PVB), having a material thickness ofapproximately 0.25-0.4 mm, are used, since the latter are also suitablefor gluing without the use of an autoclave. This in turn results in theadvantage of a substantially more energy-efficient production of thelaminated glass unit in comparison to the gluing of the layers in anautoclave.

In tests, particularly a sheet of modified EVA has proven suitable whichis commercially available under the name S-LEX-EN film from Sekusui.Instead of the plastics sheets, however, also an intermediate adhesivelayer of casting resin or silicone adhesive can be provided which has amaterial thickness of approximately 1 mm.

The afore-mentioned intermediate adhesive layers 4, 4′ may bearbitrarily combined with different intermediate adhesive layers 4, 4′to obtain a laminated glass unit 1.

Particularly for an inhomogeneous laminate, it is also suitable toprovide the sheets 8 on either side of the image layer 3 in differentnumbers of layers as said intermediate adhesive layers. For instance, asshown in FIG. 3 b, merely a single sheet 8 may be applied asintermediate adhesive layer 4 on one side, whereas two sheets 8 arearranged one on top of the other to form the intermediate adhesive layer4′ for connection with a second glass pane 2.

Besides photographs, also ink-jet, or laser prints may be used as theimage layer 3, it being possible to use different carrier materials ofthe image layers 3 in each case. To produce a transparent or translucentlaminated glass unit 1, triacetate or polyester is preferred as thecarrier material. On the other hand, for producing opaque laminatedglass units, paper, polyethylene paper or also polyester films marketedunder the trademark Melinex may, e.g., be used as the carrier materialfor the image layer 3.

When using photographs as image layer 3, preferably copies of positivesare used because of their high light-fastness on one of the previouslymentioned carrier materials, whereupon the former are developed by meansof the silver-bleaching method. In doing so, the film Ilfochrom fromIlford is particularly preferred. On the other hand, however, alsocopies of negatives may be used on one of the previously mentionedcarrier materials, yet their light-fastness is poorer.

To prevent the image layer 3 glued between the glass panes 3 frombecoming wavy, it is, however, merely essential that the twointermediate adhesive layers 4, 4′ provided for gluing are made ofdifferent materials, in particular that they have different thermalexpansion coefficients and different gluing abilities, whereby, insteadof the image layer 3 becoming wavy, the entire laminated glass unit 1becomes slightly curved upon heating, wherein, however, this curvatureis so unsubstantial that it does not negatively affect the opticalcharacteristic of the laminated glass unit.

In FIG. 4, a section of a laminated glass unit comprising two imagelayers 3 can be seen. To obtain an inhomogeneous laminate, intermediateadhesive layers 4, 4′ each of the same material and with the samematerial thickness are, indeed, provided in this exemplary embodiment,yet the glass panes 2, being e.g. 2 mm, 4 mm and 6 mm, have differentmaterial thicknesses, resulting in a different thermal expansionbehavior on each of the two sides of the image layers 3 and, thus, theimage layers 3 will reliably remain tensioned even under greatlychanging ambient temperatures, as often occurs in case of an externalapplication, e.g. when used as a facade or the like, without undesiredwaviness or blisters forming.

It goes without saying that the laminated glass unit may also comprisethree or more image layers; what is essential is merely that the imagelayers will remain tensioned even under changing ambient temperatures.

The invention claimed is:
 1. A laminated panel unit (1) comprising atleast one image layer (3) between at least two panels (2), wherein foran area-contact gluing of the image layer (3) with neighboring panels(2), one intermediate adhesive layer (4, 4′) is provided on each sidethereof, characterized in that transparent or translucent glass panesare provided as the panels (2), and that the two intermediate adhesivelayers (4, 4′) following each image layer (3) have a different thermalexpansion behavior so that the image layer (3), due to the inhomogeneouslaminate, is tensioned between the glass panes in case of temperaturechanges.
 2. A laminated panel unit according to claim 1, characterizedin that the two intermediate adhesive layers (4, 4′) are made ofdifferent materials.
 3. A laminated panel unit according to claim 1,characterized in that the two intermediate adhesive layers (4, 4′) aremade of materials having different thermal expansion coefficients.
 4. Alaminated panel unit according to claim 1, characterized in that the twointermediate adhesive layers (4, 4′) have different gluing abilities. 5.A laminated panel unit according to claim 1, characterized in that thetwo intermediate adhesive layers (4, 4′) have different materialthicknesses.
 6. A laminated panel unit according to claim 1,characterized in that at least one intermediate adhesive layer (4, 4′)is a sheet comprising at least one selected from an ethylenevinylacetate copolymer (EVA) sheet, polyvinyl acetate (PVA) sheet, andpolyvinyl butyral (PVB) sheet.
 7. A laminated panel unit according toclaim 1, characterized in that one intermediate adhesive layer (4, 4′)is made of a casting resin.
 8. A laminated panel unit according to claim1, characterized in that one intermediate adhesive layer (4, 4′) is madeof silicone adhesive.
 9. A laminated panel unit according to claim 1,characterized in that on the periphery of the panels (2), at narrowsides (6) thereof, an external insulating layer (7) is provided.
 10. Alaminated panel unit according to claim 1, characterized in that aphotograph, a slide, an ink-jet, laser or silkscreen print is providedas the image layer (3).
 11. A laminated panel unit according to claim10, characterized in that a photograph developed according to thesilver-bleaching method is provided.
 12. A laminated panel unitaccording to claim 1, characterized in that the image layer (3) istransparent, translucent or opaque.
 13. A laminated panel unit accordingto claim 1, characterized in that the laminated panel unit has an arealarger than 2 m².
 14. A laminated panel unit according to claim 9,characterized in that the external insulating layer (7) is silicone. 15.A laminated panel unit according to claim 13, characterized in that thearea is larger than 4.5 m².